This invention relates generally to disposable diapers and more particularly to an improved tape fastener system for such diapers.
Conventional disposable diapers in one popular construction are comprised of the generally rectangular absorbent pad or filler disposed between a fluid-permeable body facing top sheet and a fluid-impermeable plastic film backing sheet. The filler may be comprised of standard commercially available fluff pulp while the top sheet may be comprised of a standard commercially available nonwoven material and the backing sheet may be comprised of a thin sheet of polyethylene. At the lateral side edges of the diaper the backing sheet can be folded around the edges and sealed so that a narrow strip overlies the top sheet while at the ends of the diaper the top sheet and backing sheet can extend loosely past the top and bottom edges of the filler while being bonded together, providing a foldable flap to tuck in against the top sheet upon diapering.
A tape fastener system, in a standard construction, is comprised of a pair of pressure-sensitive fastening tapes that are adhered to the backing sheet at one end of the diaper. Usually the tapes are comprised of two separate parts with one part being the fastening tape having a fixed portion permanently bonded to the backing sheet, while the other end is the attachment portion and extends in the closed position around the side edge to overlie the separate release liner which is adhesively bonded to the top sheet. When ready for use, the attachment portion of the tape is removed from the release liner and pulled so as to extend outwardly from the side edge, thereby pulling on the plastic backing sheet with the typically exerted attaching and in-use forces.
A major problem with standard tape fastener systems that are anchored to the plastic backing sheet is when a person applies tension to the tape, stresses are created within the plastic film that often cause the film to rupture and tear, making the diaper unusable. This problem has been recognized and at least three solutions have been proposed. One solution may be seen by referring to U.S. Pat. No. 3,867,940 issued Feb. 25, 1975 to Mesek et al wherein a reinforcing scrim having a higher modulus of elasticity than the plastic film backing sheet is adhered to the thin film in a location in at least the vicinity of where the tape is adhered to the thin film. This construction allows some of the stress to be accepted by the stronger reinforcing material. Another solution may be seen by referring to U.S. Pat. No. 3,900,031 issued Aug. 19, 1975 to Endres et al, in which the fastening tapes are attached to the backing sheet in an area where the top sheet is adhered thereto along the entire top edge. In the Endres et al construction, the filler material terminates so that it does not extend all the way in a longitudinal direction to the sealed top end margin of the diaper. A third solution may be seen by referring to U.S. Pat. No. 3,848,594 issued Nov. 19, l974 to Buell in which the attachment portion is joined to a secondary tape which is then bonded to at least part of the top cover sheet creating an area of joinder adjacent the edge of the diaper so that forces imposed on the attachment portion of the tape are transmitted to both the front and back surfaces of the diaper. Each of these tape fastener constructions operate to solve the rupturing problem for a particular diaper construction; however, other solutions for various reasons are continually being sought and the present invention is another solution unlike those known in the art.
Accordingly, from the foregoing, one object of the present invention is to provide an improved diaper fastener system that reduces or eliminates tearing of the plastic film backing sheet.
Another object of the invention is to provide a diaper tape fastener system that is economical to manufacture and easy to incorporate in the diaper.
Still a further object of the present invention is to reduce tearing of the plastic backing sheet while still substantially retaining a conventional disposable diaper structure.
These and other objects of the invention will become more apparent upon reading the description to follow while referring to the drawings.